Ashwin Sankara Raman

Advisors: Prof. Gleb Yushin, Prof. Preet Singh

will defend a doctoral thesis entitled,

IN-SITU POLYMERIZED ACRYLATE-BASED SOLID ELECTROLYTES FOR LITHIUM BATTERIES

On

Friday, August 22nd at 12:30 p.m.

Closed

Committee
            Prof. Gleb Yushin – School of MSE (advisor)
            Prof. Preet Singh– School of MSE (co-advisor)
            Prof. Faisal Alamgir – School of MSE

      Prof. Matthew McDowell – School of MSE/ME

        Prof. Alexander Alexeev – School of ME

Abstract

   Current lithium battery technologies face safety risks from flammable organic solvents in liquid electrolytes, which can trigger failures and lead to fires or explosions. Solid-state electrolytes (SSEs) offer a safer alternative, with solid polymer electrolytes (SPEs) gaining attention for their stability, lithium-metal compatibility, and processing advantages. However, their limited ionic conductivity and poor electrode wetting hinder large-scale adoption.. In-situ polymerized acrylate-based SPEs provide a potential solution pathway to the above-mentioned challenges by utilizing their solvent-free processability, and ease of molecular tunability. When incorporating into lithium metal batteries (LMBs) with porous electrodes, their liquid-like wetting in solid-state provides uniform interfaces upon-polymerization, alleviating any non-uniformities in the interfaces.

    In this work, two acrylate based in-situ synthesized polymer matrices are investigated for their use in lithium-metal and lithium-ion batteries (LMBs and LIBs). The first system is based on poly(poly propylene glycol acrylate) (poly(PPGA)), a hydroxyl (-OH) terminated acrylate-based polymer. While methyl terminated monomer candidates have reported promising performance within in-situ polymerized SPE literature, hydroxyl terminated monomers have not been well understood. Dual-ion conductors using poly(PPGA) have been explored and the effect of lithium salt on the polymer matrix’s electrochemical and physical properties have been studied. Subsequently, their infiltration into porous electrodes and their functionality with lithium iron phosphate (LFP) has been evaluated. Additionally, a synergistic mechanism which combines the advantages of dual ion conductors and SLICs for improved performance in LFP||Li systems has been discovered and evaluated.

    The second system evaluated is another acrylate based in-situ polymerizeable monomer poly(polyethylene glycol methyl ether methacrylate) (poly(PEGMEMA)) consisting of an increased ethylene oxide (EO) chain length with a methyl termination. The effect of different concentrations of SLICs on the physical and electrochemical behavior of the polymer matrix is explored in comparison to dual lithium-ion conductors. Subsequently, an optimized composition of dual-ion conductors is then explored with lithium nickel manganese cobalt oxide (LiNi(1/3)Mn(1/3)Co(1/3)O2 or NMC111) cathode and graphite anode, where favorable long-term cycling performance is demonstrated. Furthermore, the viability of SLICs using this monomer through in-situ polymerization is analyzed for its physical and electrochemical properties with porous electrodes such as LFP, graphite and lithium titanium oxide (Li4Ti5O12, LTO) and its electrochemical performance is analyzed. Degradation mechanisms were identified through post-mortem analyses with this polymer matrix.